Supplementary Air Suspension Systems For Motorhomes, Horseboxes & Race-Trucks
Wiltshire, East Somerset (inc. Bath & NE Somerset), North Dorset and South Gloucestershire
So what is Supplementary Air Suspension?
What is the benefit of Supplementary Air Suspension?
A good question. Supplementary Air Suspension is also (confusingly) known as Auxiliary Air Suspension, Semi-Air Suspension or more simply, Air Assistance. So let’s start with what it is not! Full air systems replace replacing all of the vehicles road springs with air-bag/bellows type and usually the standard shock absorbers thus making it a very expensive upgrade. Supplementary systems augment the existing rear suspension only as fitted by the base-vehicle manufacturer, who normally fit a beam-type rear axle with leaf springs either side, usually only of single or twin leaves. This allows the fitment of a cost-effective, reliable system giving maximum benefit for your investment.
All the popular chassis-cabs and panel vans will have either beam axle bump-stops or spring-assistors fitted. The purpose of the former is to avoid metal-to metal contact of the axle and the chassis under extreme suspension compression, the latter is to compress and absorb some of the upward axle deflection until fully compressed, thus becoming a bump-stop at the point of full compression.
Depending on the base vehicle, these bump-stops or spring-assistors as appropriate are removed and a twin rubber bellow assembly is bolted in on both sides. Small air pipes are then routed through the vehicle to an air-valve through which the system is pressurised by a tyre inflator. With both sets of bellows pressurized, any movement of the axle relative to the chassis has an additional air cushion acting with the original springs and shock absorbers. Under spring deflection, the air bellows are compressed whereupon the internal air pressure increases in direct proportion to the amount of compression. This results in a far more cushioned ride and because each set of bellows act independently, rolling is resisted either way.
Much positive comment has been written on the Internet etc. about Supplementary Air Suspension systems with respect to Motorhomes in particular, but why?
The vast majority of motorhomes manufactured and enjoyed in Europe are built on standard van chassis such as the Fiat Ducato, Ford Transit, Peugeot Boxer, Renault Traffic, Citroen Relay and Mercedes Sprinter. Now, although these are workhorse vehicles, in their normal working life as delivery vans or commercial trade vans or chassis cabs, they spend the majority of their time at best half full but often with very little weight actually in them. If we now take the average motorhome, which has a large extended body filled with a cooker, a shower unit, beds, a fridge freezer, heaters, 2 weeks’ worth of food and drink, water tanks, all your clothes, the dog and quite literally the kitchen sink, not forgetting that case of beer that was on offer in the supermarket, what you end up with is a vehicle which is at almost its maximum laden weight all of the time. Even when it is sitting empty on your drive, you only need to compare the payload of a standard van or chassis cab to that of a motorhome to see the stress the standard suspension is under. To illustrate then:
An off the shelf Fiat Ducato MWB Chassis Cab when converted to a commercial flatbed vehicle weighs about 2000kg and has a payload of 1500kg. However, a motorhome like an Auto-Sleeper Broadway built on the same chassis has a mass in running order of 3074kg and a user payload of just 426kg. Most of that extra 1 Tonne of permanent weight is taken by the back axle!
In a surprisingly short time the rear suspension will sag and the vehicle will be travelling around with the leaf-springs in contact (or nearly) with the spring assistors or with very little actual suspension movement left in the springs before hitting the bump-stops. The Leisure Vehicle Artisan reports to owners (and often replaces) many degraded spring assistors on surprisingly low-mileage vehicles compared to their commercial counterparts.
Having any system working at maximum capacity all of the time is never a good idea and is guaranteed to shorten its life expectancy. Supplementary Air Suspension successfully alleviates this problem and brings additional benefits.
Should I have a Supplementary Air Suspension kit fitted?
In short, any Camper, Motorhome, small Light Commercial Vehicle-based Horsebox or Race-truck or normally laden panel van such as a Service Vehicle, will benefit from having a system fitted. Whilst all the suppliers/manufacturers make similar statements (as well they would), The Leisure Vehicle Artisan can promote fitment from personal experience. The LVA’s own Auto-trail Savannah Motorhome (Fiat Ducato chassis-cab at 4.25Tonnes MLW) and Business Van (Peugeot Boxer working as a Service vehicle at 3.5 Tonnes and also used for towing caravans and trailers) are both fitted with a Dunlop Supplementary Air Suspension System and the improvements are both immediate and very noticeable. In short, if you as an owner are considering upgrades to your pride and joy, a Supplementary Air Suspension System should be at the top of your list. No argument.
However, if you intend to use your rear garage, rear mounted luggage box or bike rack to the full or indeed to tow any sort of trailer, then a Supplementary Air Suspension System will aid vehicle traction. Most campers, motorhomes, small horseboxes and race-truck base vehicles are front-wheel-drive. Laws of physics dictate that weight added behind the rear axle will add an extra ‘hidden’ weight to the rear axle in proportion to the overhang, but that ‘hidden’ weight figure detracts from the front driven axle possibly lessening traction. This is of concern from a static perspective, but the dynamic weights when the vehicle is under way over say a rough/uneven road only exacerbate the situation. The fitment of a Supplementary Air Suspension System will assist in limiting these dynamic effects and therefore help in maintaining traction.
But what about vehicles built on an ALKO AMC chassis?
Whilst some Supplementary Air Suspension systems are available for ALKO AMC chassis equipped vehicles, it should be noted that the very different rear suspension arrangement is designed and manufactured to permanently carry the weight of converted motorhomes, horseboxes and race-trucks. So should a vehicle feel unstable in some way, The Leisure Vehicle Artisan would strongly suggest that the suspension may require expert diagnosis and/or the Actual Laden Weight of the vehicle (including individual axle weights) are checked on your local weighbridge before further consideration of fitting additional suspension equipment is considered. ALKO axles can and do fail occasionally, usually by seizure of one or both swing-arms. This renders the rear suspension either partially or completely non-functional. Hence the need for investigation and diagnosis if an ALKO equipped vehicle seems in need of a suspension upgrade.
However, if the axle-weight is being uprated, it is likely that companies like SVTech will recommend a Supplementary Air Suspension System. Suitable systems are available from both VB Air Suspension and ALKO Kober. Please call The Leisure Vehicle Artisan for details.
So what are the benefits that make these systems so desirable?
Everyone who owns a motorhome in particular drives somewhere at some point to enjoy their vehicle, so on road performance is as much a part of an enjoyable holiday as the standard of campsite, or the quality of your internal furnishings. The difference that a properly installed air suspension system gives is marked and instantly noticeable. The driving experience is greatly enhanced and when upgraded further with an ECU remap, the driver will be greatly impressed with the improvements to what started out as a relatively basic commercial vehicle! However the primary benefit of an air suspension system is the restoration of the original ride height. That said, it is the supplementary benefits which many people find most noticeable:
- The general ride and road handling will improve and will seem far more stable under normal conditions, notably when overtaking lorries or buses. Straight line stability on open dual-carriageways and motorways will greatly increase.
- Motorhomes and Race-trucks have high centres of gravity resulting in increased body roll. Body roll at roundabouts and when cornering is decreased (Particularly welcome in France, where the reverse road comber at roundabouts is notorious!!!), as is the sideways movement felt when in strong winds or when being overtaken by large vehicles.
- LCV based horsebox drivers will wish to reduce vehicle body roll to assist in providing their expensive but heavy equine cargo a stable and safe means of transport.
- If your vehicle has already sagged to its bump-stops, after fitment, you will notice a reduction in vibration and jarring being transmitted through the suspension to the chassis of the vehicle.
- Another important supplementary benefit is the ability to raise and lower the rear height of your vehicle by increasing/decreasing inflation pressure. This is especially useful when boarding steep ferry ramps, or negotiating kerbs or driveways. The rear valance of a motorhome is very fragile and is easily damaged in such circumstances.
The Leisure Vehicle Artisan Supplementary Air Suspension System Services:
The Leisure Vehicle Artisan can supply, fit and commission all brands of Supplementary Air Suspension Systems required by you, the customer. A Fault-finding and repair service is also offered.
What parts are required?
There are a large range of parts available for The Leisure Vehicle Artisan to suggest a reliable system that is fit-for-purpose. To start with, a vehicle specific air suspension kit is selected. These kits come with all that is required to fit the air suspension itself to the rear axle. Also included are the small-bore ait pipes that are routed to wherever the gauge and valve assembly is to be mounted. Often these are positioned in the driver’s side cab foot-well, or within the rear ski-locker of garage door.
The required position of the gauge and valve assembly will usually dictate which assembly is required, allowing for pipe entry from the left or right-hand sides, or from below. Generally these are single gauge/twin valve assemblies and only one is required.
For more convenience and depending on the base vehicle, there is a range of fascia adaptor plates which allow the gauges and valves to be within the drivers’ vision. In this instance, usually two valves and two gauges are required.
Further options include the provision and installation of a dedicated on-board air compressor such that the system air pressure can be easily adjusted. A further refinement is the addition of an air-reservoir tank, keeping the system switched on with the engine running results in completely automatic maintenance of required air pressure.
A good cost-effective and dual-purpose solution is to specify a Supplementary Air Suspension System with a single gauge/twin valve assembly, and a RAC 900 Professional High Power Air Compressor. These highly regarded compressors are often carried by UK breakdown services (AA, RAC patrols etc.) and are capable of fully inflating motorhome tyres that require 80psi, unlike most 12v tyre inflators. By connecting the RAC 900 to either the leisure battery or starting battery, one can not only adjust the Supplementary Air Suspension System, but the road wheels as well, including any trailer, towed car or motorbike. The LVA’s own Motorhome and business van are both so equipped. The Leisure Vehicle Artisan can supply new RAC 900 kits as a package with Supplementary Air Suspension Systems. Please enquire.
"This Ring RAC900 Professional High Power Air Compressor is up to 3 mins faster than a standard compressor, and has proven performance used by breakdown professionals. The RAC900 can inflate a tyre in less than 90 seconds, saving you time in an emergency. A flexible hose with quick inflator / deflator and large gradient pressure gauge that has great accuracy is exactly what you would want from a heavy duty compressor. Complete with industrial style brass nozzle, 7m coiled airline hose, quick release 12V battery clips, thermal overload protection and waterproof on / off switch."